[Physics] Dependence of the energy of an electron on distance from the nucleus

atomic-physicselectromagnetismelectronsorbitalsquantum mechanics

I was going through an article given to me by my teacher which gave info about the influence of the positive nucleus on the electrons in the 's orbital', 'p orbital' and 'd orbital' respectively.
Here I am quoting the part of the article which I didn't understand.

Despite the shielding of the outer electrons from the nucleus by the inner shell electrons, the attractive force experienced by the outer shell electrons increases with increase of nuclear charge. In other words, the energy of interaction between, the nucleus and electron (that is orbital energy) decreases (that is more negative) with the increase of the atomic number (Z).

Now after reading the article further I came across this paragraph..

The energy of electrons in s orbital will be lower (more negative) than that of p orbital electron which will have less energy than that of d orbital electron and so on.

Aren't both the above paras contradicting?

First, it says that as the electron is away from nucleus, the nucleus's influence decreases. (like it should) Then why is electron more negative? (see brackets in first para above).
Does it mean that as the electron moves away then it has less positive charge and the negative charge dominates?

But in the second para it says that the electron in s orbital (which is near nucleus) is more negative? I mean what's going on in both of these paras?

All in all I want to know,

  • Is electron near nucleus more negative/less negative and has lower energy/higher energy?


  • Is electron away from nucleus more negative/less negative and has lower energy/higher energy?

And why?

Please help me. I did genuine efforts to understand all this and surfed internet for many hours but couldn't get it.

Reference for the text quoted above: NCERT Class XI Chemistry Book, chapter 2, ยง2.6.3 (Energies of orbitals), also available as ark:/13960/t0tr17s5t.

Best Answer

The two statements are independent and not at all contradictory. Specifically:

  • For all subshells (but keeping the subshell fixed), as you increase the nuclear charge $Z$, the energy becomes more negative.
  • For a fixed nuclear charge $Z$, as you look at the different subshells of the same atom, the $s$-shell electrons will be more tightly bound (have a more negative energy) than the $p$-shell electrons.

The only way to glean a contradiction from this is to compare apples with oranges.

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